"Spread" in pair trading refers to **the difference between the closing prices of two stocks** that are part of a pair trading strategy. This strategy, often used in **quantitative finance**, involves identifying two historically correlated stocks. Traders bet on the convergence or divergence of this spread, aiming to profit from temporary pricing discrepancies. **Keywords:** pair trading, spread, quantitative finance, stock market, trading strategy, correlation, convergence, divergence.